title: Muscle fatigue during repetitive voluntary contractions: a comparison between children with cerebral palsy, typically developing children and young healthy adults.
abstract: OBJECTIVE
  To combine peak torque and EMG analyses to investigate the hypothesis that 1) children with cerebral palsy (CP) have lower muscle fatigability than typically developing children (TD) and whether 2) muscle fatigue correlates with muscle strength.
  
  
  METHODS
  Seven CP children, eight TD children and ten young healthy adults (YHA) performed an all-out fatigue test of 35 maximal concentric knee extension and flexion contractions on an isokinetic dynamometer. Angular velocity was set at 60°/s. Peak torque (PT) was determined per repetition and either normalized to bodyweight or maximum voluntary torque. Surface-EMG of quadriceps and hamstring muscles was measured to obtain changes in median frequency (EMG-mf) and smooth rectified EMG amplitude per contraction.
  
  
  RESULTS
  Decline in PT differed between all groups for extensors and flexors, where YHA showed the largest decline and CP children the smallest decline over the course of the test. YHA showed a larger decline in EMG-mf of all quadriceps and hamstrings than TD and CP children, while TD children showed a larger decline in EMG-mf of m.rectus femoris and m.vastus lateralis than CP children.
  
  
  CONCLUSIONS
  Results confirm that children with CP show lower fatigability than TD children and that the lower fatigability coincides with lower maximal muscle strength.
authors.affiliation: Department of Rehabilitation Medicine, MOVE Research Institute, VU University Medical Centre, Amsterdam, The Netherlands; Department of Research and Development, Rehabilitation Centre Heliomare, Wijk aan Zee, The Netherlands. Electronic address: m.eken@vumc.nl.
authors.forename: M M
authors.initials: MM
authors.lastname: Eken
authors.forename: A J
authors.initials: AJ
authors.lastname: Dallmeijer
authors.forename: H
authors.initials: H
authors.lastname: Houdijk
authors.forename: C A M
authors.initials: CA
authors.lastname: Doorenbosch
mesh_terms: D000293:Adolescent; D000328:Adult; D016022:Case-Control Studies; D002547:Cerebral Palsy / Q000503:physiopathology*; D002648:Child; D002657:Child Development / Q000502:physiology; D003430:Cross-Sectional Studies; D004576:Electromyography; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000502:physiology; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D024510:Muscle Development / Q000502:physiology; D018763:Muscle Fatigue / Q000502:physiology*; D053580:Muscle Strength / Q000502:physiology*; D053581:Muscle Strength Dynamometer; D018482:Muscle, Skeletal / Q000502:physiology / Q000503:physiopathology; D052097:Quadriceps Muscle / Q000502:physiology / Q000503:physiopathology*; D013848:Thigh; D019415:Torque; D055815:Young Adult
keywords: Cerebral palsy; Dynamometer; Electromyography; Muscle fatigue; Muscle strength